Understanding Your Menstrual Cycle: What Is Normal and What Is Not
Periods that are irregular, missed, or unpredictable? A calm, plain-language guide to how the menstrual cycle works, what counts as normal variation, common causes of irregularity, and when to see a doctor.
Periods are a monthly fact of life for much of a woman's life, yet how the cycle actually works — and what counts as "normal" — is rarely explained clearly. That leaves many women worrying whether their irregular, early, late, or missed periods mean something is wrong. This is a calm, plain-language guide to understanding your cycle, what normal variation looks like, common reasons periods become irregular, and when it is worth seeing a doctor.
How the Cycle Works (Simply)
Each cycle, hormones prepare the body for a possible pregnancy: an egg is released (ovulation), and the womb lining thickens. If there is no pregnancy, that lining sheds — that is your period. The whole cycle is usually counted from the first day of one period to the first day of the next. A "textbook" cycle is about 28 days, but perfectly normal cycles range roughly from 21 to 35 days, and they vary a bit from person to person and month to month.
What Is Within Normal Range
- Cycle length roughly 21–35 days
- Periods lasting about 2–7 days
- Some month-to-month variation, especially in teens and approaching menopause
- Mild cramps, and some premenstrual mood/breast changes
Common Reasons Periods Become Irregular
| Cause | Note |
|---|---|
| Puberty & perimenopause | Cycles are naturally more irregular at both ends |
| Stress, illness, big weight change | Can delay or skip periods |
| PCOS | A common hormonal cause of irregular cycles |
| Thyroid problems | An over- or under-active thyroid can affect periods |
| Contraception | Some methods change or stop periods |
| Pregnancy | The most important cause of a missed period to consider first |
Tracking Helps
Keeping a simple record — when periods start and end, how heavy, any symptoms — is genuinely useful. It shows you your own normal, helps you spot real changes, and gives a doctor far more to work with than "they're a bit irregular." A calendar or a period-tracking app both work well.
When to See a Doctor
Short of those, occasional irregularity is common and often settles. But see a gynaecologist if your pattern changes markedly, if periods are very heavy or unpredictable, or if you are trying to conceive — a doctor can check for causes like PCOS or thyroid issues and help. Understanding and tracking your cycle is empowering, and these conversations suit an online consultation well.